Flashcards in Neuro - Anat & Phys (Eye Applications Pt. 2) Deck (42):
What is miosis? With what part of the nervous system is it associated?
Miosis (constriction [of pupil], parasympathetic)
What is mydriasis? With what part of the nervous system is it associated?
Mydriasis (dilation [of pupil], sympathetic)
What are the 1st and 2nd neurons involved in Miosis? Briefly describe the route each takes.
1st neuron: Edinger-Westphal nucleus to ciliary ganglion via CN III; 2nd neuron: short ciliary nerves to pupillary sphincter muscles
What are the 1st, 2nd, and 3rd neurons involved in Mydriasis? Briefly describe the route each takes.
1st neuron: Hypothalamus to ciliospinal center of Budge (C8-T2); 2nd neuron: Exit at T1 to superior cervical ganglion (travels along cervical sympathetic chain near lung apex, subclavian vessels); 3rd neuron: Plexus along internal carotid, through cavernous sinus, Enters orbit as long ciliary nerve to pupillary dilator muscles
Describe the pathway for the Pupillary light reflex and its consequence.
Light in either retina sends a signal via CN II to pretectal nuclei (dashed lines - in visual on p. 480 in First Aid 2014) in midbrain that activates bilateral Edinger-Westphal nuclei; Pupils contract bilaterally (consensual reflex)
What can be observed clinically due to the Pupillary light reflex (if patient has normal reflex)?
Result: Illumination of 1 eye results in bilateral pupillary constriction
What causes Marcun Gunn pupil? How does it present? How is it tested?
Marcus Gunn pupil (afferent pupillary defect) - Due to optic nerve damage or severe retinal injury. Decreased bilateral pupillary constriction when light is shone in affected eye relative to unaffected eye. Tested with the "swinging flashlight test"
Draw a visual depicting the pupillary light reflex, including and labeling the following: (1) Edinger-Westphal nucleus (2) Ciliary ganglion (3) Light (4) Lateral gerniculate nucleus (5) Oculomotor nerve (6) Optic tract (7) Pretectal nucleus (8) Pupillary constrictor muscle.
See p. 480 in First Aid 2014 for visual in middle on the right
In general, what are 2 major components of CN III, and where are they located in the nerve?
CN III has both motor (central) and parasympathetic (peripheral) components.
Where does CNIII send its motor output? What category of disease primarily affects this, and why? Give an example of such a disease.
Motor output to ocular muscles - affected primarily by vascular disease (e.g., diabetes: glucose --> sorbitol) due to decreased diffusion of oxygen and nutrients to the interior fibers from compromised vasculature that resides on the outside of the nerve.
What are 2 signs of CNIII motor damage?
Signs: ptosis, "down and out" gaze
What part of CN III is first affected by compression, and why? Give 2 examples of such compression.
Parasympathetic output - fibers on the periphery are first affected by compression (e.g., posterior communicating artery aneurysm, uncal herniation)
What is the major sign of CNIII parasympathetic damage?
Signs: diminished or absent pupillary light reflex, "blown pupil" often with "down-and-out" gaze
What consequence/symptom is associated with Retinal detachment? What is the deficit, and what is its pathogenesis?
Separation of neurosensory layer of retina (photoreceptor layer with rods and cones) from outermost pigmented epithelium (normally shields excess light, support retina) --> degeneration of photoreceptors --> vision loss
What are 3 causes to which retinal detachment may be secondary?
May be secondary to retinal breaks, diabetic traction, inflammatory effusions
In what patient population are retinal breaks more common?
Breaks more common in patients with high myopia
What often precedes retinal breaks?
Often preceded by posterior vitreous detachment (flashes and floaters) and eventual monocular loss of vision like a "curtain drawn down"
How should retinal detachment be managed?
What is age-related macular degeneration, and what 2 effects does it have?
Degeneration of macula (central area of retina). Causes distortion (metamorphosia) and eventual loss of central vision (scotomas)
What is the difference between dry and wet age-related macular degeneration? How prevalent is each type?
Dry (nonexudative, > 80%); Wet (exudative, 10-15%)
What characterizes Dry age-related macular degeneration?
Dry (nonexudative, > 80%) - deposition of yellowish extracellular material in and beneath Bruch membrane and retinal pigment epithelium ("drusen") with gradual decrease in vision.
What are 2 substances used to prevent progression of dry age-related macular degeneration?
Prevent progression with multivitamin and antioxidant supplements.
What characterizes Wet age-related macular degeneration?
Wet (exudative, 10-15%) - rapid loss of vision due to bleeding secondary to choroidal neovascularization.
What are 2 treatment options for wet age-related macular degeneration?
Treat with anti-vascular endothelial growth factor injections (anti-VEGF) or laser
Draw the visual field defect (including Left and Right eyes) AND lesion associated with each of the following conditions: (1) Right anopia (2) Bitemporal hemianopia (pituitary lesion, chiasm) (3) Left homonymous hemianopia (4) Left upper quadrantic anopia (right temporal lesion, MCA) (5) Left lower quadrantic anopia (right parietal lesion, MCA) (6) Left hemianopia with macular sparing (PCA infarct), macula --> bilateral projection to occiput (7) Central scotoma (macular degeneration).
See p. 481 in First Aid 2014 for bottommost 2 visuals.
What is associated with Meyer loop? What structure does it loop around?
Meyer loop - inferior retina; Loops around inferior horn of lateral ventricle.
What is associated with the Dorsal optic radiation? Through which structure does it take the shortest path?
Dorsal optic radiation - superior retina; Takes shortest path via internal capsule.
How is an image oriented when it hits the primary visual cortex?
Note: When an image hits primary visual cortex, it is upside down and left-right reversed
What lesion can cause Bitemporal hemianopia? What structure can be affected to cause Bitemporal hemianopia?
Bitemporal hemianopia (Pituitary lesion, Chiasm)
What lesion can cause Left upper quadrantic anopia? What vessel is associated with Left upper quadrantic anopia?
Left upper quadrantic anopia (right temporal lesion, MCA)
What lesion can cause Left lower quadrantic anopia? What vessel is associated with Left lower quadrantic anopia?
Left lower quadrantic anopia (right parietal lesion, MCA)
What infarct can cause Left hemianopia with macular sparing?
Left hemianopia with macular sparing (PCA infarct)
What defect causes Central scotoma?
Central scotoma (macular degeneration)
What kind of projection comes from the macula, and to what structure does it go?
Macula --> bilateral projection to occiput
What is the Medial longitudinal fasciculus (MLF), and what function does it serve?
Medical longitudinal fasciculus (MLF): Pair of tracts that allows for crosstalk between CN VI and CN III nuclei. Coordinates both eyes to move in same horizontal direction.
Describe and explain the level of myelination on MLF.
Highly myelinated (must communicate quickly so eyes move at same time).
With what kind of condition are MLF lesions seen? Give a specific example.
Lesions seen in patients with demyelination (e.g., multiple sclerosis); Think: "MLF in MS"
What disorder does a MLF lesion causes? Explain its presentation.
Lesion in MLF = INO (Internuclear ophthalmoplegia): lack of communication such that when CN VI nucleus activates ipsilateral lateral rectus, contralateral CN III nucleus does not stimulate medial rectus to fire. Abducting eye gets nystagmus (CN VI overfires to stimulate CN III). Convergence normal.
Explain the directional term of INO (e.g., right INO, left INO).
Directional term (e.g., right INO, left INO) refers to which eye is paralyzed
Explain what events related to MLF occur as a patient looks left.
When looking left, the left nucleus of CN VI fires, which contracts the left lateral rectus and stimulates the contralateral (right) nucleus of CN III via the right MLF to contract the right medial rectus.
Draw a visual of MLF and its related pathway, including and labeling the following: (1) Nuclei of CN VI (on both sides) (2) Left MLF (3) Right MLF (4) Lateral recti (5) Medial rectus subnucleus of CN III (6) Medial recti.
See p. 482 in First Aid 2014 for visual on left